1. Preheat oven to 350 degrees F. Grease an 8x8" or 9" round pan. Rinse and drain beans in a strainer. In empty bean can, scoop in 1/2 bean can’s worth beans out of the strainer and transfer to a food processor.
2. Once you’ve done that, fill the can 1/2 full with water and add that to processor. Blend until there are no beans, lumps, or bumps.
3. Add banana to the processor and blend again until there are no chunks of anything left. Set aside. In a mixing bowl, whisk together flour, cocoa, sugar, baking powder, and salt.
4. Add bean-banana mixture plus the coffee and vanilla to dry ingredients, along with the chocolate chips. Mix until there are no more lumps. Pour batter in prepared pan, and bake for 25 minutes.
Source of recipe: I messed around with a recipe from No Meat Athlete. My version of the recipe appears on my blog: http://healthykitschyvegan.wordpress.com/2011/08/03/the-secret-life-of-bs/